Embodiments of the present disclosure generally relate to implantable medical devices, and more particularly to antenna and attachment mechanisms for use with rechargeable implantable medical devices.
An implantable medical device (IMD) is a medical device that is implanted in a patient to, among other things, monitor electrical activity of a heart, and optionally to deliver therapy. An IMD may record cardiac activity of a patient over time and report such cardiac activity to an external device. The IMD device may optionally perform various levels of sophisticated analysis of the cardiac activity and based thereon perform additional recording operations. The IMD may also be configured to deliver appropriate electrical and/or drug therapy. Examples of IMDs include cardiac monitoring devices, pacemakers, cardioverters, cardiac rhythm management devices, defibrillators, neurostimulators and the like. The electrical therapy produced by an IMD may include, for example, pacing pulses, cardioverting pulses, and/or defibrillator pulses. The device is used to both provide treatment for the patient and to inform the patient and medical personnel of the physiologic condition of the patient and the status of the treatment.
In general, an IMD includes a battery, memory and electronic circuitry that are hermetically sealed within a metal housing (generally referred to as the “can”). The metal housing typically is formed of titanium and includes a shell with an interconnect cavity, in which the memory, pulse generator and/or processor module reside. The device housing is configured to receive a header assembly. The header assembly comprises a mechanical structure which houses an antenna and a sensing electrode. A feedthrough assembly is located at a header receptacle area and is sealed to the device housing to form an interface for conductors to enter/exit the interconnect cavity.
Some IMDs communicate with external devices and/or other implanted devices through an RF antenna. One of the primary requirements for an RF antenna operating within an implantable medical device is to fit within the small size of a device header while maintaining a satisfactory level of RF performance. Conventional IMDs include an antenna that coexists with other metallic structures in the header such as leads and connector blocks.
However, recent developments with rechargeable IMDs have presented an additional challenge. In at least one proposed rechargeable IMD, a charge coil is provided in the device header where the charge coil comes into close proximity with the antenna. The charge coil both restricts the size of the antenna and creates a potential RF coupling effect with the antenna. The coupling effect causes RF energy to leak out of the antenna to the coil where the RF energy is lost. The coupling effect decreases the signal power exhibited by the antenna thereby degrading RF performance.
Conventional antennas utilize antenna configurations that do not fit within the tight space requirements of a rechargeable IMD when the charge coil in the header. Further, conventional IMD antenna, such as the monopole or loop antennas, suffer undue degradation due to RF coupling when the charge coil is added to the header.
A need remains for a new type of antenna that is both small and does not experience undue performance degradation in the presence of nearby metal objects like a charge coil.
Further, conventional attachment mechanisms that couple the antenna to a feedthrough experience certain limitations. In particular, conventional attachment mechanisms complicate the assembly and manufacturing process.
A need remains for an improved attachment mechanism between the feedthrough assembly and electronic components within the device header.